Bifurcated stent and method for the manufacture and delivery of same

ABSTRACT

An expandable bifurcated stent comprising a proximal end and a distal end in communication with one another. The proximal end comprises a primary passageway and the distal end comprises a pair of secondary passageways. The stent is expandable from a first, contracted position to a second, expanded position upon the application of a radially outward force exerted on the stent. Each of the primary passageway and the secondary passageway being constructed of has a porous surface. A method for production of a bifurcated stent is also described. Preferably, the method comprises the step of connecting a first stent section to a second stent section, the first stent section having an end thereof adapted for connection to an opening disposed along the length of a second stent section.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bifurcated stent, and to a method forthe manufacture and delivery of a bifurcated stent.

2. Description of the Prior Art

Stents are generally known. Indeed, the term "stent" has been usedinterchangeably with terms such as "intraluminal vascular graft" and"expansible prosthesis". As used throughout this specification the term"stent" is intended to have a broad meaning and encompasses anyexpandable prosthetic device for implantation in a body passageway(e.g., a lumen or artery).

In the past six to eight years, the use of stents has attracted anincreasing amount of attention due the potential of these devices to beused, in certain cases, as an alternative to surgery. Generally, a stentis used to obtain and maintain the patency of the body passageway whilemaintaining the integrity of the passageway. As used in thisspecification, the term "body passageway" is intended to have a broadmeaning and encompasses any duct (e.g., natural or iatrogenic) withinthe human body and can include a member selected from the groupcomprising: blood vessels, respiratory ducts, gastrointestinal ducts andthe like.

Initial stents were self-expanding, spring-like deviccs which wereinserted in the body passageway in a contracted state. When released,the stent would automatically expand and increase to a final diameterdependent on the size of the stent and the elasticity of the bodypassageway. Such stents are known in the art as the Wallstent™.

The self-expanding stents were found by some investigators to bedeficient since, when deployed, they could place undue, permanent stresson the walls of the body passageway. This lead to the development ofvarious stents which were controllably expandable at the target bodypassageway so that only sufficient force to maintain the patency of thebody passageway was applied in expanding the stent.

Generally, in these later systems, a stent, in association with aballoon, is delivered to the target area of the body passageway by acatheter system. Once the stent has been properly located (the targetarea of the body passageway can be filled with a contrast medium tofacilitate visualization during fluoroscopy), the balloon is expandedthereby expanding the stent, e.g. by plastic deformation of the stentstructure, so that the latter is urged in place against the bodypassageway. As indicated above, the amount of force applied is at leastthat necessary to maintain the patency of the body passageway. At thispoint, the balloon is deflated and withdrawn within the catheter, andsubsequently removed. Ideally, the stent will remain in place andmaintain the target area of the body passageway substantially free ofblockage (or narrowing).

A stent which has gained some notoriety in the art is known as thePalmaz-Schatz™ Balloon Expandable Stent (hereinafter referred to as "thePalmaz-Schatz stent"). This stent is discussed in a number of patentsincluding U.S. Pat. Nos. 4,733,665, 4,739,762, 5,102,417 and 5,316,023,the contents of each of which are hereby incorporated by reference.

Another stent which has gained some notoriety in the art is known asGianturco-Roubin Flex-Stent™ (hereinafter referred to as "theGianturco-Roubin stent"). This stent is discussed in a number of patentsincluding U.S. Pat. Nos. 4,800,882, 4,907,336 and 5,041,126, thecontents of each of which are hereby incorporated by reference.

Other types of stents are disclosed in the following patents:

U.S. Pat. No. 5,035,706 (Gianturco et al.),

U.S. Pat. No. 5,037,392 (Hillstead),

U.S. Pat. No. 5,147,385 (Beck et al.),

U.S. Pat. No. 5,282,824 (Gianturco),

Canadian patent 1,239,755 (Wallsten), and

Canadian patent 1,245,527 (Gianturco et al.),

the contents of each of which are hereby incorporated by reference.

All of the stents described in the above-identified patents share thecommon design of being mono-tubular and thus, are best suited to bedelivered and implanted in-line in the body passageway. These knownstents are inappropriate for use in a bifurcated body passageway (e.g. abody passageway comprising a parent passageway that splits into a pairof passageways). Further, these stents are inappropriate for use in abody passageway having side branches since: (i) accurate placement ofthe stent substantially increases the risk to the patient, (ii) the riskof passageway closure in the side branches is increased, and (iii) theside branches will be substantially inaccessible.

Indeed the Physician Guide published in support of the Palmaz-Schatzstent states on page 32 (the contents of which are hereby incorporatedby reference):

". . . no attempt should be made following placement of a PALMAZ-SCHATZstent to access the side branch with a guide wire or a balloon, as suchattempts may result in additional damage to the target vessel or thestent. Attempts to treat obstructed side branches within stentedsegments can result in balloon entrapment, necessitating emergencybypass surgery."

Thus, when installed, the Palmaz-Schatz stent admittedly shields sidebranches emanating from the target area of the body passagewayeffectively permanently. This can be problematic since the only way totreat blockage or other problems associated with the side branches is toperform the type of surgery which installation of the stent was intendedto avoid.

This contraindication for conventional mono-tubular stents iscorroborated by a number of investigators. See, for example, thefollowing:

1. Interventional Cardiovascular Medicine: Principles and Practice(1994); Publisher: Churchill Livingstone Inc.; pages 221-223 (Ohman etal.), 487-488 (Labinaz et al.), 667-668 (Bashore et al.) and 897 (Baileyet al.), including references cited therein;

2. Gianturco-Roubin Flex-Stent™ Coronary Stent: Physician's Guide; page2, Paragraph 3 under WARNINGS;

3. Circulation, Vol. 83, No. 1, January 1991 (Schatz et al.); entitled"Clinical Experience With the Palmaz-Schatz Coronary Stent"; pages148-161 at page 149; and

4. American Heart Journal, Vol. 127, No. 2, February 1994 (Eeckhout etal.); entitled "Complications and follow-up after intracoronarystenting: Critical analysis of a 6-year single-center experience"; pages262-272 at page 263,

the contents of each of which are hereby incorporated by reference.

Further, some investigators have attempted to install individual stentsin each branch of the bifurcated body passageway. However, this approachis fraught with at least two significant problems. First, implantationof three individual stents, together with the expansive forces generatedupon implantation results in subjecting the central walls of thebifurcated body passageway to undue stress which may lead topost-procedural complications. Second, since the central walls of thebifurcated body passageway are not supported by the individual stents,this area of the passageway is left substantially unprotected andsusceptible to blockage.

One particular problem area with bifurcated body passageways is theoccurrence of bifurcation lesions within the coronary circulation.Generally, these legions may be classified as follows:

    ______________________________________                                        Type      Characteristic                                                      ______________________________________                                        A         Prebranch stenosis not involving the ostium of                                             the side branch;                                       B                     Postbranch stenosis of the parent vessel not                                   involving the origin of the side branch;               C                     Stenosis encompassing the side branch but not                                  involving the ostium;                                  D                     Stenosis involving the parent vessel and ostium                                of the side branch;                                    E                     Stenosis involving the ostium of the side branch                               only; and                                              F                     Stenosis discretely involving the parent vessel                                and ostium of the side branch.                         ______________________________________                                    

See Atlas of Interventional Cardiology (Popma et al.), 1994, pages77-79, the contents of which are hereby incorporated by reference. Thepresence of bifurcation lesions is predictive of increased proceduralcomplications including acute vessel closure.

Detailed classification of other bifurcated body passageways isrelatively undeveloped given the lack of non-surgical treatmentapproaches.

U.S. Pat. No. 4,994,071 (MacGregor) discloses a bifurcating stentapparatus. The particular design incorporates a series of generallyparallel oriented loops interconnected by a sequence of "half-birch"connections. The lattice structure of the illustrated stent isconstructed of wire. The use of such wire is important to obtain theloop structure of the illustrated design. The use of a wire loopconstruction is disadvantageous since it is complicated to manufactureand the resulting stent is subject to expansion variability (e.g.variable post-expansion distortion and the like).

U.S. Pat. Nos. 3,993,078 (Bergentz et al.) and 5,342,387 (Summers) alsodisclose and illustrate a bifurcated stent design constructed of wire.These designs suffer from the same disadvantages as the design describedin the previous paragraph.

It would be desirable to have a reliable, expandable bifurcated stentsince this would be useful in treating aneurysms, blockages and otherailments. It would be further desirable to have a practical method forproducing such a stent. It would also be desirable if such a stent wasrelatively easy to install.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel expandablebifurcated stent which obviates or mitigates at least one of theabove-mentioned disadvantages of the prior art.

It is another object of the present invention to provide a novel methodfor the manufacture of an expandable bifurcated stent.

It is another object of the present invention to provide a novel methodfor implanting an expandable bifurcated stent.

Accordingly, in one of its aspects, the present invention provides anexpandable bifurcated stent comprising a proximal end and a distal endin communication with one another, the proximal end comprising a primarypassageway and the distal end comprising a pair of secondarypassageways, each secondary passageway in communication with the primarypassageway at a first intersection, the stent being expandable from afirst, contracted position to a second, expanded position upon theapplication of a radially outward force exerted on the stent, each ofthe primary passageway and the secondary passageways being constructedof a tubular wall having a porous surface, at least one connectionportion being disposed at the first intersection for reinforcing thefirst intersection.

In another of its aspects, the present invention provides expandablebifurcated stent comprising a proximal end and a distal end incommunication with one another, the proximal end comprising a primarypassageway and the distal end comprising a pair of secondarypassageways, each secondary passageway in communication with the primarypassageway at a first intersection, the stent being expandable from afirst, contracted position to a second, expanded position upon theapplication of a radially outward force exerted on the stent, each ofthe primary passageway and the secondary passageways having a poroussurface, at least one connection portion interconnecting the pair ofsecondary passageways for reinforcing the first intersection.

In yet another of its aspects, the present invention provides a methodfor production of a bifurcated stent comprising the step of connecting afirst stent section to a second stent section, the first stent sectionhaving an end thereof adapted for connection to an opening disposedalong the length of a second stent section.

In yet another of its aspects, the present invention provides a methodfor production of a bifurcated stent comprising the steps of:

(i) connecting a first stent section to a second stent section toprovide a connection portion;

(ii) provide an opening in the connection portion;

(iii) connecting a third stent section to the connection portion.

In yet another of its aspects, the present invention provides a methodfor production of a bifurcated stent comprising the steps of:

passing a first stent section having a first opening disposed along alength thereof through a second stent section having a second openingdisposed along a length thereof, the first stent section having adiameter less than a diameter of the second stent section;

passing a leading end of the first stent section through the secondopening of the second stent section; and

substantially aligning the first opening and the second opening withrespect to one another.

In yet another of its aspects, the present invention provides a methodfor delivery to a target body passageway of an expandable bifurcatedstent comprising a proximal end and a distal end in communication withone another, the proximal end comprising a primary passageway and thedistal end comprising a pair of secondary passageways, the stent beingexpandable from a first, contracted position to a second, expandedposition upon the application of a radially outward force exerted on thestent, each of the primary passageway and the secondary passageway beingconstructed of a tubular wall having a porous surface, the methodcomprising the steps of:

disposing the stent in the first, contracted position on a catheter;

inserting the stent and catheter within the target body passageway bycatheterization of the target body passageway;

exerting a radially outward expansive force on the stent such that thestent assumes the second, expanded position and is urged against thetarget body passageway.

In yet another of its aspects, the present invention relates to anexpandable bifurcated having a longitudinal axis, the stent comprising aproximal end and a distal end in communication with one another, theproximal end comprising a primary passageway and the distal endcomprising a pair of secondary passageways, each secondary passageway incommunication with the primary passageway at a first intersection, thestent being expandable from a first, contracted position to a second,expanded position upon the application of a radially outward forceexerted on the stent, the intersection comprising a circumferentialregion consisting of: (i) points of connection between the primarypassageway and the secondary passageway, and (ii) an area of overlapbetween the primary passageway and the secondary passageway, the primarypassageway and the secondary passageway being moveable with respect toone another in a direction substantially parallel to the longitudinalaxis.

In this aspect of the invention, it has been discovered that an improvedbifurcated stent can be produced by judicious design of the region ofthe stent near the intersection of the various stent sections.Specifically, at this intersection, it is desirable to provide acircumferential region having: (i) connection points which hold thestent together, and (ii) at one area of overlap between the primarypassageway and the secondary passageway. The connection points aredisposed in the circumferential region between respective areas of theprimary passageway and the secondary passageway which are not stressedwhen the stent is flexed. The area of overlap between the primarypassageway and the secondary passageway in the circumferential region isdisposed between respective areas of the primary passageway and thesecondary passageway which are stressed when the stent is flexed. Forthis reason, there is no connection between the primary passageway andthe secondary passageway in the "area of overlap". Thus, when the stentis flexed, the primary passageway and the secondary passageway are ableto move longitudinally with respect to one another thereby enhance theflexibility of the unexpanded stent. In other words, in the unexpandedstate, the area of overlap functions as a longitudinally slidable joint.When the stent is expanded, the area of overlap serves to reinforce thecircumferential region of the intersection thereby mitigating recoil ofthe stent and/or restenosis.

Thus, an aspect of the present invention relates to the provision of anexpandable bifurcated stent constructed of a tubular wall having aporous surface. As used throughout this specification, the term "tubularwall", when used in relation to a stent, is intended to mean asubstantially cylindrical tube which subsequently has been subjected toan etching (e.g. by laser, chemical or other suitable means) or similartechnique to remove pre-selected portions of the cylindrical tubethereby providing a porous surface on the tube--this is distinct from astent constructed of wire bent to a selected shape/design. To theknowledge of the Applicant's, an expandable bifurcated stent having sucha tubular wall has heretofore been unknown.

As used throughout this specification, the term "bifurcated stent" isintended to have a broad meaning and encompasses any stent having aprimary passageway to which is connected at least two secondarypassageways. Thus, trifurcated stents are encompassed herein. Further,one of the secondary passageways can be a continuation of the primarypassageway with the result that the other secondary passageway isessentially a side branch to the primary passageway.

The Applicant's have also discovered that various repeating patterns inthe porous surface of the tubular wall are particularly advantageous.Generally, the repeating pattern is a polygon having a pair of sidewalls substantially parallel to the longitudinal axis of the stentpassageway in question, a first concave-shaped wall and a secondconvex-shaped wall connecting the side walls. The various repeatingpatterns which are useful in the context of the present invention aredisclosed in the following copending patent applications filed in thename of the assignee of the present invention:

Canadian patent application number 2,134,997 (filed Nov. 3, 1994);

Canadian patent application number 2,171,047 (filed Mar. 5, 1996);

Canadian patent application number 2,175,722 (filed May 3, 1996);

Canadian patent application number 2,185,740 (filed Sep. 17, 1996);

International patent application PCT/CA97/00151 (filed Mar. 5, 1997);and

International patent application PCT/CA97/00152 (filed Mar. 5, 1997);

the contents of each of which are hereby incorporated by reference(hereinafter collectively referred to as the "Divysio patentapplications").

The present bifurcated stent may be constructed from any suitablestarting material. Preferably, the starting material is a thin tube of ametal or alloy (non-limiting examples include stainless steel, titanium,tantalum, nitinol, Elgiloy, NP35N and mixtures thereof) which would thenhave sections thereof cut or etched out to leave a repeating pattern,inter alia, such as one or more of those disclosed in the Divysio patentapplications.

The stent of the present invention may further comprise a coatingmaterial thereon. The coating material may be disposed continuously ordiscontinuously on the surface of the stent. Further, the coating may bedisposed on the interior and/or the exterior surface(s) of the stent.The coating material may be one or more of a biologically inert material(e.g. to reduce the thrombogenicity of the stent), a medicinalcomposition which leaches into the wall of the body passageway afterimplantation (e.g. to provide anticoagulant action, to deliver apharmaceutical to the body passageway and the like) and the like.

The stent is preferably provided with a biocompatible coating, in orderto minimize adverse interaction with the walls of the body vessel and/orwith the liquid, usually blood, flowing through the vessel. The coatingis preferably a polymeric material, which is generally provided byapplying to the stent a solution or dispersion of preformed polymer in asolvent and removing the solvent. Non-polymeric coating material mayalternatively be used. Suitable coating materials, for instancepolymers, may be polytetraflouroethylene or silicone rubbers, orpolyurethanes which are known to be biocompatible. Preferably, however,the polymer has zwitterionic pendant groups, generally ammoniumphosphate ester groups, for instance phosphoryl choline groups oranalogues thereof. Examples of suitable polymers are described inpublished International patent applications WO-A-93/16479 andWO-A-93/15775. Polymers described in those specifications arehemo-compatible as well as generally biocompatible and, in addition, arelubricious. When a biocompatible coating is used, It is important toensure that the surfaces of the stent are completely coated in order tominimize unfavourable interactions, for instance with blood, which mightlead to thrombosis.

This good coating can be achieved by suitable selection of coatingconditions, such as coating solution viscosity, coating technique and/orsolvent removal step.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be described with reference tothe accompanying drawings wherein like numerals designate like parts andin which:

Embodiments of the present invention will be described with reference tothe accompanying drawings wherein like numerals designate like parts andin which:

FIG. 1 illustrates a side elevation of a bifurcated stent in accordancewith the present invention;

FIGS. 2-4 illustrate a first embodiment of a method for production of abifurcated stent;

FIG. 5 illustrates a second embodiment of a method for production of abifurcated stent;

FIGS. 6a and 6b illustrate a post-treatment of a bifurcated stent whichhas been produced according to the methods illustrated in FIGS. 2-5;

FIGS. 7 and 8 illustrate a third embodiment of a method for productionof a bifurcated stent;

FIG. 9 illustrates a post-treated bifurcated stent which has beenproduced according to the method illustrated in FIGS. 7 and 8;

FIGS. 10 and 11 illustrate a fourth embodiment of a method forproduction of a bifurcated stent;

FIG. 12 illustrates a cross-section of a bifurcated body passageway intowhich the a bifurcated stent produced according to the present method ofmanufacture is being delivered;

FIG. 13 illustrates a cross-section of a bifurcated body passageway inwhich the bifurcated stent is positioned in a first, contractedposition;

FIG. 14 illustrates a cross-section of a bifurcated body passageway inwhich the bifurcated stent is positioned in a second, expanded position;

FIGS. 15 and 16 illustrate a side elevation of another bifurcated stentin accordance with the present invention;

FIGS. 17-22 illustrate various preferred features of the bifurcatedstent illustrated in FIGS. 15 and 16; and

FIGS. 23-24 illustrate an enlarged of a mode of attaching the stentsections illustrated in the embodiment of the present method illustratedin FIGS. 7-9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, there is illustrated a stent 10. Stent 10comprises a proximal end 15 and a distal end 20. Proximal end 15comprises a primary passageway 25. Distal end 20 comprises a pair ofsecondary passageways 30,35. Secondary passageways 30,35 are connectedto primary passageway 25 at an intersection point 40. As will beapparent to those of skill in the art, stent 10 incorporates the poroussurface design illustrated in copending Canadian patent applicationnumber 2,134,944, referred to above. As discussed above, this design maybe varied to incorporate other designs such as those disclosed in theother Divysio patent applications.

With reference to FIGS. 2-4, an embodiment of the present method forproduction of a bifurcated stent is illustrated. For ease ofillustration, the porous surface of the tubular wall of the stent is notillustrated.

As illustrated, a first stent section 45 comprises a cylindrical tubehaving a bevelled cut 50 made adjacent one end of the cylindrical tube.Those of skill in the art will recognize that bevelled cut 50 may beincorporated into first stent section 45 during or after the productionof first stent section 45. Specifically, it is possible to produce firststent section 45 having a pre-selected porous design which includesbevelled cut 50 via a computer programmable, high precision laseretching technique. Alternatively, it is possible to use another etchingtechnique to produce first stent section 45 without bevelled cut 50 andthereafter use a precision jig or other means to cut first stent section45 to produce bevelled cut 50.

Similarly, a second stent section 55 is provided and includes radialcuts 56,57 and a longitudinal cut 58. Radial cuts 56,57 and longitudinalcuts 58 may be produced in second stent section 55 in the mannerdiscussed in the previous paragraph with respect to the production ofbevelled cut 50 in first stent section 45. Thereafter, a flap portion 51of first stent section 45 is folded away from bevelled cut 50.Similarly, a pair of flap 52,53 are folded away from longitudinal cut 58to expose an opening 54.

First stent section 45 is then lowered to cover opening 54 of secondstent section 55. Flaps 52,53 are folded to overlap a portion of firststent section 45. Flap 51 is folded to overlap a portion of second stentsection 55. With reference to FIG. 4, it is particularly preferred toadapt the geometry of flaps 52,53 of second stent section 55 such thatvarious of the struts disposed in flaps 52,53 overlap with or arejuxtaposed (in plan view) along at least a portion of the length thereofwith the struts on first stent section 45 (this is illustrated in moredetail hereinbelow with reference to FIG. 16). Preferably, the degree ofsuch overlap or juxtaposition is sufficient to:

(i) facilitate affixing the flaps 52,53 of second stent section 55 tofirst stent section 45;

(ii) achieve uniform expansion of the stent junction without occurrenceof substantial distortion; and

(iii) avoid the occurrence of "stent trap" or "stent jail" (usually theresult of cracking, buckling or other distortion at the junction of adeployed bifurcated stent making dificult or impossible to deliver afurther stent through the stent).

At this point, the flaps may be secured to the respective stent sectionsby any suitable means such as spot welding (e.g. by a laser or othersuitable means), loops, clips and the like. The preferred method ofaffixing the flaps to the respective stent section is to spot weld them.

A particular advantage of the process illustrated in FIGS. 2-4 is thatintersection point 40 (FIG. 1--overlapping flaps not illustrated forclarity) of the resulting. stent is reinforced by virtue of dispositionof the flaps overlapping a portion of the respective stent sections.

As will be apparent to those of skill in the art, in certaincircumstances, it may be possible and even desirable to reduce the sizeof or even eliminate flap 51. Further, in certain circumstances, it maybe possible or ever desirable to trim one or both of flaps 52,53 priorto connection of first stent section 45 to second stent section 55.

With reference to FIG. 5, there is illustrated another embodiment of thepresent method for manufacture of a bifurcated stent. In thisembodiment, flap 51 (FIGS. 2 and 3) is simply cut away from first stentsection 45a. Further, an oval opening 54a is cut into second stentsection 55a (i.e. there are no flaps affixed to second stent section55a). Stent section 45a is then lowered on and connected to second stentsection 55a. First stent section 45a and second stent section 55a may beconnected to another in the manner described hereinabove with referenceto FIGS. 2-4.

With reference to FIG. 6a, there is illustrated the stent produced bythe methods illustrated in FIGS. 2-5. During production of the stent, itis desirable to minimize the angle between first stent section 45 andsecond stent section 55. Even with this effort, it is preferred that theadjacent termini of first stent section 45 and section stent section 55are subjected to application of gentle squeezing or other sufficientforce in the direction of arrows A to facilitate catheterization of thestent. The result of such post-production treatment of the stent isillustrated in FIG. 6b.

With reference to FIGS. 7 and 8, there is illustrated yet anotherembodiment of the present method for manufacture of a bifurcated stent.In this embodiment, a pair of first stent sections 45b are secured oraffixed to one another. Thereafter, an apex portion 46b of the resultingconstruction is removed exposing an opening 54b. A second stent section55b is then connected to opening 54b provided by the combination offirst stent sections 45b. The manner of securing second stent section55b to the periphery of opening 54b created by first stent sections 45bis not particularly restricted and may be effected as discussedhereinabove. As will be appreciated by those of skill in the art, it ispossible and, in certain circumstances, desirable, to have one or moreflaps on one or move of first stent sections 45b and second stentsection 55b. Such flaps would be used in the manner discussedhereinabove in respect of FIGS. 2-4 to overlap a portion of the oppositestent section.

With reference to FIG. 9, there is illustrated the stent producedaccording to the method illustrated in FIGS. 7 and 8 afterpost-treatment in the manner discussed above in respect of FIGS. 6a and6b. That is, first stent sections 45b are subjected to application ofgentle squeezing or other sufficient force in the direction of arrows Bto facilitate catheterization of the stent.

Of course, it is possible to modify the detail of the embodimentillustrated in FIGS. 7-9 without departing from the spirit and scopethereof. For example, instead of affixing first stent sections 45b asillustrated, it is possible to start with a single tube and dispose aradial cut therein to cut a portion of the circumference of the tube(i.e., as will be described, a connection tab remains on the tube) andthereafter bending back the termini of the tube toward each to produce aV-shaped (or U-shaped) arrangement as illustrated in FIG. 7--i.e., thisresults in the production of pair of stent sections connection to oneanother by the connection tab. When the stent sections are bent back,the define opening 54b in FIG. 7 to which second stent section 55b canbe attached.

With reference FIGS. 23-24, there is illustrated a preferred manner ofaffixing section stent section 55b to opening 54b of the embodimentillustrated in FIG. 7. In FIGS. 23-24, reference will be made to one ofthe specific designs in the Divysio patent applications. However, thoseof skill in the art will immediately recognize that the embodimentillustrated in FIGS. 23-24 can be adapted with other stent designs.

In FIG. 23 there is illustrate an enlarged two-dimensionalrepresentation of a wall 200 of opening 54b and a wall 250 at the end ofsecond stent section 55b. Wall 200 comprises an undulating pattern 205.Undulating pattern 205 comprises a plurality of connection points 210.Wall 250 comprises an undulating pattern 255. Undulating pattern 255comprises a plurality of connection points 260. In the illustratedembodiment, between adjacent connection points 260 there is disposed atab 265.

When it is desired to connect the walls, wall 200 may be moved towardwall 250 in the direction of arrow G to achieve overlap betweenundulating patterns 205 and 255 as illustrated in FIG. 24. This allowsresults in overlap between connection points 210 and 260. At this pointa laser weld or other affixation technique is used to connection walls200 and 250 to one another at connection points 210 and 260. Walls 200and 250 are not connected to each other at tab 265. Thus, when theresulting bifurcated stent is flexed, walls 200 and 250 are relativelyunstressed in the region of connection points 210 and 260. Additionally,the location of connection points 210 and 260 is selected such that theyare unstressed during expansion of the stent--this is apparent in FIG.23. In the region of tab 265 (i.e., where walls 210 and 250 are notconnected to one another), walls 200 and 250 are moveable with respectto the direction of arrow H.

Additionally, when the bifurcated stent is expanded, tab 265 providesoverall reinforcement of the stent in the circumferential region of theintersection which reduces the occurrence of stent recoil and/orrestenosis (e.g., at blockages 170,175 discussed hereinbelow withreference to FIG. 12).

Of course, those of skill in the art will recognize that the preciseshape and size of tab 265 is not particularly restricted and can bevaried to vary the degree of reinforcement conferred to the stent afterexpansion thereof.

With reference to FIGS. 10 and 11, there is illustrated yet anotherembodiment of the present method for manufacture of a bifurcated stent.In this embodiment, a first stent section 45c is provided with anopening 54c. A second stent section 55c is provided with an opening 56c.Second stent section 55c has a diameter slightly less than that of firststent section 45c. The difference in diameter between first stentsection 45c and second stent section 55c is sufficient to enable coaxialmovement of the stent sections with respect to one another with causingdamage to either stent section.

As illustrated by arrow C in FIG. 10, the end of second stent section55c is coaxially fed into an end of first stent section 45c. Once theleading end of second stent section 55c reaches opening 54c of firststent section 45c, it is pulled through opening 54c as illustrated byarrow D in FIG. 10. Second stent section 55c is pulled through opening54c until opening 56c is aligned with opening 54c--this is illustratedby dashed oval E in FIG. 11.

When practising the method illustrated in FIGS. 10 and 11, care shouldbe taken to design openings 54c and 56c so that they are in alignmentwhen the trailing end of second stent section 55c is flush with thetrailing end of first stent section 45c. Further, region F (FIG. 11) ofthe resulting bifurcated stent is "double reinforced" since it containsa coaxial disposition of first stent section 45c and second stentsection 55c. Accordingly, it is possible and, in some cases evendesirable, to modify the design of the respective stent sections in thisregion so that the overall expansion and relative flexibility/rigidityof the stent in this region is commensurate with that of the remainingportion of the stent (i.e. the secondary passageways which branch offfrom region F in FIG. 11). While the embodiment illustrated in FIGS. 10and 11 illustrates the resultant bifurcated stent having a coaxial,overlapping arrangement of stent sections flush at one end, it will beappreciated by those of skill in the art that the length of first stentsection 45c or second stent section 55c may be shortened therebyminimizing the size of region F in FIG. 11.

With reference to FIGS. 12-14 , there is illustrated a bifurcated bodypassageway 150 comprised of a proximal passageway 155 and a pair ofdistal passageways 160,165. As illustrated, bifurcated body passageway150 comprises a Type "D" Bifurcation lesion having characteristicblockages 170,175,180.

Stent 10 is delivered to bifurcated body passageway 150 in the followingmanner. Initially, a pair of guidewires 185,190 are inserted intoproximal passageway 155 such that guidewire 185 enters distal passageway160 and guidewire 190 enters distal passageway 165. The manner by whichthe guidewires are inserted is conventional and within the purview of aperson skilled in the art.

As illustrated, stent 10 is positioned in association with a pair ofcatheters 195,200 (for clarity, the interior of stent 10 is not shown).Catheter 195 has associated with it a balloon 205. Catheter 200 hasassociated with it a balloon 210. Balloons 205,210 substantially fillprimary passageway 25 of stent 10. Balloon 205 substantially fillssecondary passageway 30 of stent 10. Balloon 210 substantially fillssecondary passageway 35 of stent 10.

The stent/catheter/balloon combination is delivered through proximalpassageway 155 with the aid of guidewires 185,190. As thestent/catheter/balloon combination approaches distal passageways160,165, predisposition of guidewires 185,190 serves to separatesecondary passageways 30,35 to be disposed in distal passageways160,165, respectively. Thus, as illustrated in FIG. 13, stent 10 ispositioned in place.

Once stent 10 is in position, balloons 205,210 are expanded resulting inimplantation of stent 10 in the corresponding interior surfaces ofproximal passageway 155 and distal passageways 160,165. Uponimplantation of stent 10, balloons 205,210 are collapsed. Thereafter,catheters 195,200 and guidewires 185,190 have been removed leaving theimplanted stent 10 shown in FIG. 14. As illustrated in FIG. 14,blockages 170,175,180 are bulged radially outwardly in combination withthe appropriate portions of proximal passageway 155 and distalpassageways 160,165 resulting in a reduction in the overall blockage inbifurcated body passage 150.

It will be apparent to those of skill in the art that implantation ofstent 10 can be accomplished by various other means. For example, it iscontemplated that it is possible to substitute the pair ofcatheter/balloon combinations illustrated in FIGS. 12 and 13 with asingle, bifurcated catheter/balloon design which mimics the design ofthe stent. Thus, in this modification, the balloon and guidewire wouldbe design to mimic the bifurcated design of the stent. As furtheralternative, it is contemplated that the stent can be made of a suitablematerial which will expand when bifurcated body passageway 150 isflushed with a liquid having an elevated temperature (e.g. 150° F.-160°F.). Further, stent 10 can be designed to expand upon the application ofmechanical forces other than those applied by a balloon/catheter. Stillfurther, stent 10 can be designed self-expanding (e.g. by constructingstent from material such as nitinol and the like) to be implanted asdescribed above. In this embodiment, the radially outward force exertedon the stent would be generated within the stent itself.

With reference to FIGS. 15-22, there is illustrated another preferredbifurcated stent in accordance with the present invention. As will beapparent to those of skill in the art, the stent illustrated in FIGS.15-22 shares many of the features of stent 10 illustrated in FIG. 1.

Thus, with reference to FIGS. 15 and 16, there is illustrated a stent100. FIG. 15 is a side elevation of stent 100 without the porous surfaceillustrated (for clarity). FIG. 16 is a side elevation of an enlargedportion of stent 100 with the porous surface illustrated. Stent 100comprises a proximal end 102 and a distal end 104. Proximal end 102comprises a primary passageway 103. Distal end 104 comprises a pair ofsecondary passageways 105,106. Secondary passageways 105,106 areconnected to primary passageway 103 at an intersection point 107--thenature of intersection point 107 will be further discussed hereinbelow.It is intersection point 107 which distinguishes stent 100 in FIG. 16from stent 10 in FIG. 1.

As will be apparent to those of skill in the art, stent 100 incorporatesthe porous surface design illustrated in copending Canadian patentapplication number 2,134,944, referred to above. As discussed above,this design may be varied to incorporate other designs such as thosedisclosed in the other Divysio patent applications.

With reference to FIGS. 17-19, manufacture of stent 100 will bediscussed. Generally, the manufacture of stent 100 is similar to themanufacture of stent 10 illustrated in FIGS. 1-4 and discussedhereinabove. The principle difference in the manufacture of stent 100 isthe use of a modified first stent section 108.

First stent section 108 is constructed from a substantially cylindricaltube 109. A porous surface 110 is disposed on a major portion ofcylindrical tube 109. A first connection tab 111 and a second connectiontab 112 are also disposed on cylindrical tube 109. As discussedhereinabove, it is possible to produce first section 108 comprisingporous 110, first connection tab 111 and second connection tab 112 usingcomputer programmable, high precision laser etching techniques or byother etching techniques in combination with precision jig techniques.This results in an end of porous surface 110 comprising first connectiontab 111, second connection tab 112 and a bevelled edge 113. The productof the cutting techniques is illustrated in FIG. 18.

FIG. 19 is an enlarged perspective view of a portion of first connectiontab 111 (second connection tab 112 is preferably the same). Asillustrated, first connection tab 111 comprises a stem 114 and a head115. Preferably, stem 114 and/or head 115 are curved to have a shapecomplementary to the outer surface of the second section to which firststent section 108 is connected (discussed in more detailed hereinbelow).Stem 114 and head 115 comprise a plurality of slots 116 disposedtherein. Slots 116 may be disposed in stem 114 and head 115 by the useof a computer programmable, high precision laser as described above.Preferably, slots 116 are disposed throughout the thickness of stem 114and head 115. Slots 116 may be may have a straight or taperedcross-section. Preferably, slots 116 have a thickness in the range offrom about 0.0015 to about 0.004 inches. Head 115 further comprisessolid (i.e., slot-free or non-porous) regions 117,118.

Thus, in the embodiment illustrated in FIG. 19, slots 116 serve to froma porous surface in first connection tab 111 (second connection tab 112is preferably the same). While it is preferred to have such a poroussurface disposed in the connection tabs, the precise nature of theporosity is not particularly restricted. The provision of a poroussurface, particularly at head 115, facilitates expansion of theconnection tab while minimizing or avoiding the occurrence of crackingor distortion.

After the production of first stent section 108, first connection tab111 and second connection tab 112 are bent or otherwise moved to besubstantially collinear with the periphery of bevelled edge 113 (i.e.,as illustrated in FIG. 118). At this point, first stent section 108 maybe connected to another stent section of a design similar to secondstent section 55 discussed hereinabove with reference to FIGS. 2-4--seeintersection point 107 in FIG. 16. In this embodiment, as in theembodiments illustrated in FIGS. 2-4, it is preferred to adapt thegeometry of flaps 52,53 of second stent section 55 such that various ofthe struts disposed in flaps 52,53 overlap along at a portion of thelength thereof with the struts on first stent section 108. See, forexample, regions G and H in FIG. 16 which illustrates an embodiment ofsuch partial overlap and juxtaposition (in plan view). First connectiontab 111 and second connection tab 112 may be secured to the second stentsection as described above. Specifically, it is particularly preferredto connect solid (i.e., non-porous) regions 117,118 to the stent sectionportion.

The benefits accruing from the use of first stent section 108 in theproduction a bifurcated stent include:

1. The provision of at least one solid (i.e., non-porous) region in theconnection tabs facilitates attachment of the respective stent sectionsto one another (e.g., laser welding is facilitated significantly);

2. The provision of a porous surface in at least a portion of theconnection tabs facilitates bending thereof for connection of therespective stent sections; and

3. The provision of slots 116, particularly in second connection tab 112(see FIG. 15), allows the slots to function as a solid state valve atthe "crotch" of the bifurcated stent thereby providing sealed,reinforcement of the bifurcated stent in this crucial region--this isillustrated in FIG. 20 which depicts tapered openings for slots 116 inthe apex of the bend in stem 114.

FIG. 21 illustrates an alternate embodiment of the embodimentillustrated in FIGS. 15-20. Specifically, in FIG. 21, second stentsection 55, otherwise the same as that described hereinabove withreference to FIGS. 1-4, is adapted to include a landing 119 forreceiving a solid (i.e. non-slot or non-porous) connection tab 120.Landing 119 may be connected to connection tab 120 as describedhereinabove.

With reference to FIG. 22, there is illustrated a variant to theembodiment illustrated in FIG. 21. Specifically, in FIG. 22, aconnection tab 121 having the entire surface thereof slotted andotherwise porous is connected to landing 119.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications of the illustrative embodiments,as well as other embodiments of the invention, will be apparent topersons skilled in the art upon reference to this description. Forexample, while first connection tab 111 and second connection tab 112have been illustrated as being attached to first stent portion 108, itis possible to have these tabs integral with second stent portion 55.Alternatively, the connection tabs do not have to integral with eitherof the stent portions and, instead, can be custom-designed, independentconnection tabs which are affixed to both stent portions. Still further,it is possible for the connection tabs (integral or independent) to havea different thickness than either of the stent sections. It is thereforecontemplated that the appended claims will cover any such modificationsor embodiments.

What is claimed is:
 1. An expandable bifurcated stent having alongitudinal axis, the stent comprising a proximal end and a distal endin communication with one another, the proximal end comprising a primarypassageway and the distal end comprising a pair of secondarypassageways, each secondary passageway in communication with the primarypassageway at a first intersection, the stent being expandable from afirst, contracted position to a second, expanded position upon theapplication of a radially outward force exerted on the stent, theintersection comprising a circumferential region consisting of: (i)points of connection between the primary passageway and the secondarypassageway, and (ii) an area of contacting overlap between the primarypassageway and the secondary passageway, the primary passageway and thecontacting area in the secondary passageway being moveable with respectto one another in a direction substantially parallel to the longitudinalaxis.
 2. The bifurcated stent defined in claim 1, wherein the area ofoverlap is defined by a first area on the primary passageway and asecond area on the secondary passageway.
 3. The bifurcated stent definedin claim 2, wherein the first area is disposed within the second area.4. The bifurcated stent defined in claim 2, wherein first area isdefined by a substantially elongate tab.
 5. The bifurcated stent definedin claim 4, wherein the substantially elongate tab has a head and abody, the head being radially wider than the body.
 6. The bifurcatedstent defined in claim 1, comprising at least two areas of overlap. 7.The bifurcated stent defined in claim 1, comprising two areas ofoverlap.
 8. The bifurcated stent defined in claim 7, wherein the twoareas of overlap are substantially diametrically opposed to one anotherin the circumferential region.
 9. The bifurcated stent defined in claim1, wherein the pair of secondary passageways are integrally connected toone another by a segment.
 10. The bifurcated stent defined in claim 1,wherein the stent comprises a first stent section connected to a secondstent section.
 11. A method for production of a bifurcated stentcomprising the steps:cutting a portion of a circumference of a firststent section, the uncut portion of the circumference defining aconnection tab; translating opposed ends of the first stent sectiontoward one another to define a first opening along the length of thefirst stent section; and connecting a second stent section to firststent section at the opening.
 12. The method defined in claim 11,wherein the translating step comprises bending the connection tab. 13.The method defined in claim 11, wherein the cutting step comprises anon-linear radial cut to define a serrated first opening.
 14. The methoddefined in claim 13, wherein the non-linear radial cut is asubstantially sinusoidal radial cut.
 15. The method defined in claim 13,wherein the non-linear cut is a substantially undulating radial cut. 16.The method defined in claim 11, wherein the connecting step comprisespositioning the first stent section and the second section stent sectionto define an area of overlap therebetween.
 17. The method defined inclaim 16, wherein the connecting step comprises selectively connectingthe first stent section to the second stent section in the area ofoverlap.
 18. The method defined in claim 16, wherein said positioningcomprises disposing the second stent section within the first stentsection to define the area of overlap.
 19. The method defined in claim11, wherein the connecting step comprises welding the first stentsection to the second stent section.